The present invention is concerned with bonded media. Certain inorganic materials are sometimes present in a form in which they are difficult to handle and use. For example, basic oxygen steelmaking sludge (which is a waste product from the basic oxygen steelmaking process), contains up to 30% moisture and solids, including ferrous sulfide, iron oxide and various foundry additives, as well as other metals such as zinc.
Basic oxygen steelmaking sludge is generally considered to be a waste product, for which disposal is very expensive and difficult, partly because of its zinc content. We have now devised a way of using such basic oxygen steelmaking sludge, and other mineral and inorganic materials.
According to the present invention therefore, there is provided a method of forming thermally shock stable bonded solid materials, which comprises mixing a solid mineral or inorganic material in an aqueous medium with a lignosulfonate, treating the aqueous medium with a polyvalent or polydentate cationic complexing agent for lignosulfonate, with application of heat sufficient to maintain said lignosulfonate in fluid form, so as to produce an intimate mix of said complexing agent with said lignosulfonate and said mineral or inorganic material, and thoroughly mixing the resulting substantially dry material with a substantially dry further reagent comprising urea or a urea derivative, so as to cause the mix to agglomerate.